CA1084613A - Steered lateral course transition control for aircraft area navigation systems - Google Patents
Steered lateral course transition control for aircraft area navigation systemsInfo
- Publication number
- CA1084613A CA1084613A CA247,526A CA247526A CA1084613A CA 1084613 A CA1084613 A CA 1084613A CA 247526 A CA247526 A CA 247526A CA 1084613 A CA1084613 A CA 1084613A
- Authority
- CA
- Canada
- Prior art keywords
- signal
- aircraft
- respect
- track
- computing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D1/00—Control of position, course or altitude of land, water, air, or space vehicles, e.g. automatic pilot
- G05D1/02—Control of position or course in two dimensions
- G05D1/0202—Control of position or course in two dimensions specially adapted to aircraft
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S1/00—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith
- G01S1/02—Beacons or beacon systems transmitting signals having a characteristic or characteristics capable of being detected by non-directional receivers and defining directions, positions, or position lines fixed relatively to the beacon transmitters; Receivers co-operating therewith using radio waves
- G01S1/08—Systems for determining direction or position line
Abstract
ABSTRACT OF THE DISCLOSURE
Control apparatus for an aircraft area navigation system computes a predetermined curved path from the inbound course to the outbound course of the waypoint or the inbound course to the next waypoint and provides aircraft steering signal with regard to the predetermined curved path. A bank angle bias command is applied to the apparatus for effecting transition from the inbound course to the curved path and is removed when the aircraft transitions from the curved path to the outbound course. Cross track and track angle error signals are generated with regard to the predetermined curved path for steering the aircraft thereon as the course transition is effected.
Control apparatus for an aircraft area navigation system computes a predetermined curved path from the inbound course to the outbound course of the waypoint or the inbound course to the next waypoint and provides aircraft steering signal with regard to the predetermined curved path. A bank angle bias command is applied to the apparatus for effecting transition from the inbound course to the curved path and is removed when the aircraft transitions from the curved path to the outbound course. Cross track and track angle error signals are generated with regard to the predetermined curved path for steering the aircraft thereon as the course transition is effected.
Description
BACKGROUND OF THE INV~NTION
1. Field of the Invention The invention generally relates to aircraft area naviga-tion systems, particularly with regard to effecting lateral transitions with regard to the waypoints of the flight plan.
1. Field of the Invention The invention generally relates to aircraft area naviga-tion systems, particularly with regard to effecting lateral transitions with regard to the waypoints of the flight plan.
2. DescriPtion of the Prior Art -Aircraft area navigation systems, hereinafter referred to as RNAV, are known in the prior art that transition the air-craft from the inbound course or leg of a waypoint to the next leg thereof by merely switching from the first track to the . . .
next at a predetermined distance from the waypoint and permit-ting the steering signals to capture the next leg by either -manual pilot control through the flight director or by apply-ing the steering signals to the automatic flight control system. This prior art procedure, particularly in the auto-matic mode, provides an exponential capture of the next track utilizing a blend of cross track deviation and track angle error. Since the prior art approach assumes the absence of non-linearities such as roll attitude limits ~unrestricted bank angle commands) and, in practice, the bank angle commands are necessarily limited ~or safety and passenger comfort, undesirable overshooting or hunting ("S" turning) o~ the next leg results there~y utilizing an excessive amount o air space in a relatively uncontrolled manner. Additionally, at the point o~ leg switching larye deviation signals are generated which re~ult in presenting an undesirable large deviation indication and a sudden shift ln the commanded heading to the human pilot via the flight instruments. When the displayed deviation is at or near its maximum value, the pilot i8 unable to maintain cognizance o~ the aircra~t position. Although this prior art track transitioning technique ha~ satisEied aviation regulatory agency present day re~uirements with regard to , " , ,~ ," ~ ' ' , ..
, '` las~6~3 aircraft spacing when transitioning from one course to another, potential precise future requirements of "guidance around corners" with regard to air-craft spacing will not be so satisfied.
A predetermined curved path is computed from one leg to the next leg in an RNAV system and steering signals are generated with regard to the curved path to guide the aircraft therealong. A bank angle bias command is ~ -utilized in defining the curved path during the leg transition. Cross track and track angle error signals are generated with regard to the curved path.
These signals may be applied to the automatic flight control system and/or ~
to the flight instruments to effect automatic control and to apprise the ~ -human pilot of the aircraft attitude and position with regard to the curved path so that corrective action may be effected.
~,;
Thus it is appreciated that the aforedescribed disadvantages of the prior art technique are eliminated in a manner to be clarified hereinafter.
The invention concerns apparatus for use in an area nayigation system for aircraft for controlling the transition of the aircraft from an ;
inbound course to an outbound course of a waypoint. The apparatus comprises a bank bias circuit for generating a bank angle command signal for rolling the aircraft to a desired bank attitude. The apparatus further includos a curved path computing circuit or computing a curved path from the inbound course to the outbound course in accordance with the bank angle command signal. A deviation circuit is included for generatlng deviation signals with respect to the curved path for constraining the aircraft to fly the curved path in executing the transition from the inbound to the outbound course.
~ igure 1 is a diagram illustrating geometrical parameters with regard to the curved transition path from an inbound course to an outbound course at a waypoint;
Figure 2 is a diagram similar to ~igure 1 illustrating further geometrical para~eters;
~igure 3 is a schematic block diagram of curved transitlon path ,~', .
, . . . . .
, ... . . .
`` 1~)84~3 generation and control apparatus for an aircraft area navigation system instrumented in accordance with the invention;
Figure 4 is a graph depicting the functional relationship of -desired bank angle with regard to ground speed and track change angle; and -2a-, 1~)8~ 3 1 Fig. 5 is a schematic block diagram o an alternative embodiment of the invention.
DESCRIPTION OF T~E PREFERRED EMBODIMENTS
Referring to Figs. 1 and 2, the lateral navigation para- -meters associated with transitioning from the inbound course to the outbound course of a waypoint of an RNAV system is illustrated. A waypoint 10 whose geographical location is determined in a well known manner by the r, ~ coordinates with respect to a VORTAC 11 has an inbound course 12 and an out-bound course 13 associated therewith. The inbound and outbound courses 12 and 13 with respect to north are designated ab ~ 1 and ~ 2 respectively. The geographical location of an aircraft 14 is determined from the VORTAC 11 in a conventional manner by the R, Q coordinates illustrated. The north and east components of the locations of the waypoint 10, the VORTAC 11 and the aircr~ft 14 with respect to each other are also illus-trated. For example, the north and east coordinate= of the aircrat 14 with respect to the VORTAC 11 are indicated in Fig.
2 as NAV and EAV respectively. Similarly the north and east coordinates of the waypoint 10 with re5pect to the VORTAC 11 are de~ignated as NWV and EWV respectively. Furthermore, NAW
and EAW designate the north and east coordinates o the aircrat 14 with respect to the waypoint 10.
In accordance wit~ the invention, a curved path 15 is generated along which to 1y the aircrat 1~ to eect a smooth and controlled transition from the inbound course 12 to the out~
bound cour~e 13. Preerably the curved path 15 is circular and ~, tangential to the inbound and outbound cour~es at points A and B respectively. ~ maximum aircrat ban~ anyle for the tran~ition ~o is determined as a function o aircrat ground ~peed and angular dierence between the inbound and outbound course~. With the 1 bank angle determined, a turning radius 16 or the curved path 15 is established in accordance with the maximum bank angle and the aircrat ground speed. The distance d is then determined which locates the point A on the inbound course 12 and in combination with the turn radius 16 locates the turn center for the curved path 15.
In order for the aircraft 14 to fly the path 15, the maximum bank angle is established at point A with the aircraft returning to zero bank angle at point B. However, since the aircraft 14 cannot be rolled into and out of t~e maximum bank attitude instantaneously, the associated roll command is , applied and removed at points A' and Bl respectively. The distances d' from the points A' and B' are determined rom considerations o~ passenger comfort and aircra~t roll response in accordance with the speciic aircraft to which the invention is applied.
With the aircraft 14 at the commanded bank angle at point A, the craft heading rate maintains the aircrat on the curved path 15 in an idealized calm air environment. However, due to winds, velocity changes, trim conditions, and the like, the aircrat 14 will deviate from the curved path 15. In order to correct or these deviations the cross track error (XTK) and the track angle error ~TKE) with respect to the curved path 15 are generated to steer the aircrat and provide pilot displays in a manner to be descri~ed~ For ease o lllustration with regard to Fig. 1, the aircrat 14 is oten considered to be located at point A. Thus the north and east coordinates o~ the aircra~t 14 with regard to the turn center are designated as NTCA and ETCA respectively. Similarly, NTCW and ETC~I designate the north and east components o t~e turn center with respect to the waypoint 10.
, . , ,: , .
`` l.V~G13 -1 Re~errinq to Fig. 3 with continued reference to Figs. 1 and 2, a schematic block diagram of apparatu~ for generating the curved path 15 and for controlling the aircraft 14 to fly therealong in transitioning from the inbound cour~e to the outbound course of the waypoint 10, is illustrated. The apparatu~
of Fig. 3 includes a plurality of function blocks that may be implemented by any of a variety of well known devices. For example, the function blocks may be instrumented by special purpose discrete analog or digital circuits or may alternatively be implemented by yeneral purpose digital computation apparatus.
A VOR re~eiver 20 provides thè VOR bearing J~ and a DME
receiver 21 provides the DME distance R in response to the signals from the VORTAC 11. The distance and bea~ing data are applied to a function block 22 wherein a function Fl converts the VO~ and DME data to the north and east coordinates, NAV
and EAV respectively, of the aircraft with respect to the VORTAC 11. Circuits for providing the function ~1 are well --known in ~he art and will not be described further herein for br0vity. The VOR and DME data are also applied to function blocks 23 and 24 wherein conventional circuitry implementing functions F2 and F3 provide the track angle and the ground speed V respectively of the aircrat 14. It will be appreciated that aircrat heading ~HDG) from a conventional compass system 29 and true airspeed (TAS) from a conventional air data system 28 may be utilized as inputs to the function block 2~ thereby generating a current and accurate value of the ground speed V.
The function F3 of the block 24 may be implemented as disclosed in U.S. patent 3,919,529 is~ued November 11, 1975 in the names o Donald H. Baker and ~arry ~. ~owe entltled "Radio Navigation System" and a~signed to the as~ign~e o the present invention.
~, , : . , .
. .
'; '";'''','' ' 1~ i13 1 The appara~us o~ Fig. 3 also lncludes a computer 25 for storing the navigational data with regard to the flight plan of the aircraft. For example, the computer 25 may be preloaded prior to a particular flight with the geographical locations of all of the waypoints along the ~light plan as well as the locations of the associated VORTACs. The computer is arranged in a conventional manner to provide the required data as the aircra~t executes the flight plan with regard to the sequentially - encountered waypoints. For example, with the aircra~t on the inbound course 12 of the waypoint 10, the computer 25 provides the pre-stored inbound and outbound courses ~1 and ~2 respectively ~or the waypoint 10 as well as the bearing O and distance r of the waypoint 10 with respect to the VORT~C 11.
The computer 25 also provides a control signal CCW in accord-ance whether the turn from the inbound course 12 to the out-bound course 13 is clockwise or counter-clockwise.
The computer 25 receives signals from a pilot manual data input device 26 by which the pilot may alter the data stored in the computer 25 or may enter new data therein. The device 26 may, for example, be implemented as a conventional alphanumeric and discrete data keyboard entry device for providing the data to the computer 25 in a well known manner~
The davice 26 may be utilized, ~or example, when the pilot wishes to deviate ~rom the ~light plan as stored in the computer 25.
The beæing and distance data (O, r) o~ the waypoint 10 with respect to the VORT~C 11 is applied to a ~unction block 27.
The block 27 in a well known manner instruments a conventional ~unction F4 ~or converting the O,r data to the north and east coordinates ~WV and EWV re~pect~vely o~ the waypoint with regard , 8~ L3 1 to the VORTAC. The signals NAV from the block 22 and NWV from the block 27 are applied to an algebraic summing device 30 to provide the north coordinate N~W of the aircraft 14 with respect to the waypoint lO. Similarly, the E~V signal from -the block 22 and the EWV signal from the block 27 are applied to an algebraic summing device 31 to provide the east coordinate EAW of the aircraft 14 with respect to the waypoint lO.
The inbound and outbound course signals ~ 1 and Y2 from the computer 25 as well as the ground speed signal V from the function block 24 are applied to a function block 32. The function block 32 provides the ma~imum desired bank angle 0m in accordance with a functional relationship F5 of the track change A~= ~2- ~1 and the ground speed V. The desired bank angle 0m is determined substantially as the pilot would from aircraft speed and the magnitude of the heading change. The faster the aircraft is moving, the lower the desired bank angle should be to provide a "smooth" ride. The larger the required heading change, the steeper the desired bank angle should be for prac~ical reasons. The bank angle command 0m is applied ;
at point ~' ~Fig. 1) such that the aircraft will have assumed the bank angle when it reaches point A, thus causing the craft to execute the curved path 15 in a manner to be describedO
It will be appreciated that the unctional relationship F5 implemented by the bloc~ 32 is ~elected in accordance with the particular characteristics o the aircra~t in which the system is in~talled. Reerriny to Fig. ~, typical functional relation~hip~ suitable or u~e in modern ~et transports are illu~trated. Functional relationship lines a, b, c, d and e repre~ent track change~ o 7 9O, 70, 50, 30 and ~ 10 respectively. The ifunctional relationship~ o~ Fig. ~ are "j, . . .. .. .. ... . . . . . .
1 readily implemented by such conventional devices as storage tables, diode matrices and the like. It will be appreciated that the block 32 also contains a difference circuit for obtaining a~= ~2- ~1 and this difference signal together with the ground speed V from the block 24 addresses the function generating apparatus to provide the associated value 0m as illustrated in Fig. 4.
Referring again to Fig. 3, the bank angle signal ~m from the block 32 and the ground speed signal V from the block 24 are applied to a function bloc~ 33 to generate the turn radius (TR) 16 (Fig. 1) for the circular path 15 in accordance with a function F6 as follows: 2 -~ .
F6 = TR = g tan ~
where g is the gravity constant. As previously described, it is appreciated that the function F6 is readily instrumented by any of a variety of suitable and well known analog and digital circuits.
The ~1 and ~ 2 signals rom the computer 25 as well as the turn radius signal TR from the function block 33 are applied 2~ to a function block 34 to generake a signal "d" in accordance with the distance between the point A and the waypoint 10 o Fig~ 1. The distance d is generated in accordance with a function F7 as ollows:
F7 - d = TR T~N 2 where, as previouslY discus5ed~ a ~= ~2- ~1' The implemented in any convenient manner in accordance with the unction F7 as discussed above with regard to t~e block 33.
The ~1 signal rom t~e computer 25, t~e turn radius TR
signal from the unction block 33 and the d ~ignal from the lVb~;13 1 function block 34 are applied to a function block 35 to generate the north and east coordinates of the turn center location with respect to the waypoint 10 as illustrated in Fig. 2, in accord- -ance with a function F8 as follows:
¦~TCW = -d cos ~1 ~ TR sin ~1 L~TCW = -d sin ~1 + TR cos ~1 The block 35 is implemented in any convenient manner as ~ -described above with respect to the block 33.
The NTCW signal from the block 35 and the N~W signal from the algebraic summing device 30 are combined in an alge~raic summing device 36 to provide the NTCA north coordinate of the aircraft location with respect to the turn center. In a ~;
similar manner, an algebraic summing device 37 combines the ETCW signal from the block 35 with the EAW signal from the algebraic summing device 31 to provide the ETC~ coordinate , -signal of the aircraft location with respect to the turn center.
The NTCA and ETCA signals are applied as inputs to a function block 40 wherein the quantity ~1 as illustrated in Fig. 1 is generated in accordance with a ~unction Fg as ollows:
Fg = ~1 = TAN 1 ETCA
where e1 represents the angular position of the aircraft on -the curved pat~ 15.
The track angle signal from the unction block 23, the CCW signal rom the computer 25 and the ~1 signal rom the function bloc~ 40, as well as a constant signal representing 90 are applied to a function block 41 to ~enerate the track angle error TKE in accordance with a function F1o as follows:
(TKE ~ ~ 90) - TR~CK ~NGLE or CCW tu~ns 10 ~ KE = (el~ 90) - TRACK ANGLE FOR CW turns , '' '' ',' ,, ,, ' ' , ' , ~ " ' ' ' ' , ' , , . . .
lV8¢~3 The TKE signal is applied to a line 42 as well as to a gain block 43. The gain block 43 applies a gain k2 to the TKE
signal in a well known manner, the gain being selected and .
conventionally adjusted in accordance with the aircraft characteristics and velocity..
The CCW signal from the computer 25, the turn radius signal TR ~rom the function block 33, the NTCA signal from the summing device 36 and the ETCA signal from the summing device 37 are applied to a function block 44 for generating 10 the cross track error signal ~KT in accordance with a function F11 as follows: .
XTK = ~NTCA + ETCA2 - TR for CCW turns XTK = TR - ~TCA ~ ETC~ for CW turns The XK~r signal is applied to a lead 45 as well as to a gain :
block 46 which inparts a gain k1 to the XKT signal in a manner similar to that described with respect to the block 43. The gain adjusted ~K signal from the block 46 is combined with the 0m signal from the block 32 in an algebraic summing device 47. The output of the algebraic summing device 47 and the gain 20 adjusted TKE signal rom the block 43 are combined in an algebraic summing device 50 to provide the system steering singal 0c on a lead 51. The 0c signal may be expressed as ollows:
0c '0~ ~ kl X~['K t k2 TKE
Preferably the steering signal 0c on the lead 51 is applied to the roll channel of the aircraft automatic flight control system and al~o to the lateral steering cue o~ the attitude director indicator of the 1ight director system o the crat. The track angle error signal TKE on the lead 42 is 30 pre:eerably applied to the commanded heading bug of the lVt~13 1 horizontal situation indicator instrument of the aircraft while the cross track error signal XTK on the lead 45 is applied to the lateral deviation indicator of the horizontal situation indicator. ~ --In operation, when the aircraft reaches the point A' (Fig. 1) as indicated by the signal d from the block 34 and the above discussed predetermined value of d', aircrat control is switched by conventional means not shown from the straight line control apparatus for the inbound course 12 (Fig. 1) to the curved path control apparatus of Fig. 3. The 0m signal from the block 32 applied via elements 47 and 50 to the lead 51 causes the aircraft to assume the bank angle ~m at the point ~.
The bank angle 0m then causes the craft to endeavor to turn ~ -about the turn center as determined by the NTCA and ETCA signals from the elements 36 and 37 respectively with a turn radius TR ~ -as determined by the block 33. When the craft is on the curved -path 15 the track angle error signal on the lead 42 and the cross track error signal on the lead 45 are both zero and thus the steering command 0c is equal to the bank angle command 0m which tends to maintain the craft on the curved path 15 by maintaining the craft banksd at the angle 0m. When the craft departs rom the curved path 15, due or example to transients .
such as wind and the li~c~ or aircraft configuration changes, t~e combination of the track angle error rom the block 41 and the cross track error slgnal from the block 44 combined in the steering command 0c tend to steer the aircraft back to the curved path 15.
~ hen the craft reaches the point ~' (Fig. 1) as deter-minea from the computed value of ~ and the predetermined value o dl a~ ai~cUssea above, aircraf~ control i5 ~witched ~
, . :. ,. ", . ~ " , . . . . . .
.... .. . . . . . . .
" , ' , .. . . . .
:l~J~ 13 1 means not shown -Erom the curved path control apparatus o~ -Fig. 3 to the straight line control apparatus with regard to the outbound course 13 and thus the aircraft rolls back to wings level flight by the time it reaches point B, completing the transition from the inbound course 12 to the outbound course 13 of the waypoint 10.
It will be appreciated that since the cross track error from the block 44 is applied via the lead 45 to the lateral deviation cue of the horizontal situation indicator (HSI) and since the error is computed with respect to the curved path 15 as the aircraft executes the course transition, it is merely necessary that the pilot maintains the lateral deviation indicator centered in order to make good the desired curved -path. Similarly, since the track angle error from the block 41 is applied via the lead 42 to the commanded heading bug of the HSI and the error is computed with respect to the curved path 15, the commanded heading bug remains centered under the index of the HSI as the craft executes the course transition along the curved path 15. The turn rate o the cra~t along the curved path 15 is displayed to the pilot by reason o the compass card o the HSI slewing under the commanded heading bug at a rate equal to the turning rate o the cra~t until the new course is achieved at point B o Fig. 1. Thus the present invention guides the aircra~t in making turns by utilizing the same ~teering laws and outputs as when flying straight tracks, and additionally permit~ consistent HSI display rules. Thus it i~ appreciated that the HSI di~plays to the pilot a clear and uninterrupted presentation o the system perormance throughout the tran8ition.
Reerring now to Fig. 5 in w~lich like reerence numerals ~, . ..
' ', ' . "~ '' ', "",~ ' " ',, ' ', , ' .
~o~
1 indicate like components with respect to Fig. 3, an alternative embodiment of the invention is illustrated. The VOR receiver 20, the DME receiver 21 and the pilot manual data input device --- -26 provide inputs to a programmed general purpose digital computer 60, the data inputs from the blocks 20, 21 and 26 being similar to those described above with respect to Fig. 3. It will be appreciated that conventional analog-to-digital conver-ters (not shown) may be utilized at the input interface of the computer 60 where appropriate. The computer 60 is programmed to provide the track angle error signal TKE, the cross track error XTK and the steering signal 0c on the leads 42, 45 and 51 respectively, the nature and purposes of these signals having been previously described with respect to Fig. 3.
The computer 60 is programmed in a conventional and well known manner to provide the N~V, FAV, track angle and ground speed (V) signals as described above from the VOR and DME data.
. .
Additionally, in a manner similar to that described above with regard to the computer 25 o Fig. 3, the computer 60 stores the ~ 2~ ~ r and CCW data with regard to the VORT~Cs and waypoints of the flight plan. The5e data may also be altered and supplemented by the pilot manual dcata input device 26 ln the manner previously described. The computer 60 is furthermore programmed in a conventional and well ~nown manner to provide the NWV and ~WV signals ~rom the ~ and r data stored therein~
With the above described parcameters internally available, the computer 60 is programmed to provide the 0c~ the X~K and the TKæ signal~ in accordance with the following program Chapin Chart:
1()8~ i3 PROGRAM CHAPIN CHART
. . . . . . .... ._ __ . .. .. : .
NAW = NAV -- NWV
. _. _ . . . .
EAW - EAV - EWV
. . . _ . . .
~ 2 ... . . . . ..... ____ . . .. _ _._ _ __ 0m= ~ (V~ Q~) .
g t~n 0m _ d = TR * TAN a Yl NTCW = -d*cos ~1 - TR sin 1 - I : - :
ETCW = -d*sin ~Yl + TR*cos ~1 ~TCA = NTCW - NAW ~ .
- I
ETCA = ETCW -- EAW
~:
~ = T~-l NTCA
: ~ - ~ I . .
: : Tru~ CCW = 1~ ~alse¦
~ ~ XTK = ~CA2 -TR };~K = TR - ~/~rCA~ ETCAZ
: . . . . I
1 : rKE = ~Ql-90)- TP~ACK ANGI~E TKE = t0l~9O)- TRACK ANGLE
~ . . .. . . . _ ___ I
0c ~ 0m ~ kl *~K ~ k2*TKE
' . ' ~.
:
. ..
--1~
- .
. . . .
,~, , ',"' ',, ' . ' ' .
lU6~
1 As is known to those skilled in the art, the program chapin chart represents a convenient format, similar to the familiar program flow chart, for organizing the details of the computations to be performed preparatory to coding by the programmer. It will furthermore be readily appreciated by those skilled in the art that coding is generated in a routine manner from the above chapin chart in any convenient programming language associated with the computer utilized and will not be further described herein for brevity. It will be appreciated that the 0m data is computed in a manner similar to that described above with regard to the function block 32 of Fig.
next at a predetermined distance from the waypoint and permit-ting the steering signals to capture the next leg by either -manual pilot control through the flight director or by apply-ing the steering signals to the automatic flight control system. This prior art procedure, particularly in the auto-matic mode, provides an exponential capture of the next track utilizing a blend of cross track deviation and track angle error. Since the prior art approach assumes the absence of non-linearities such as roll attitude limits ~unrestricted bank angle commands) and, in practice, the bank angle commands are necessarily limited ~or safety and passenger comfort, undesirable overshooting or hunting ("S" turning) o~ the next leg results there~y utilizing an excessive amount o air space in a relatively uncontrolled manner. Additionally, at the point o~ leg switching larye deviation signals are generated which re~ult in presenting an undesirable large deviation indication and a sudden shift ln the commanded heading to the human pilot via the flight instruments. When the displayed deviation is at or near its maximum value, the pilot i8 unable to maintain cognizance o~ the aircra~t position. Although this prior art track transitioning technique ha~ satisEied aviation regulatory agency present day re~uirements with regard to , " , ,~ ," ~ ' ' , ..
, '` las~6~3 aircraft spacing when transitioning from one course to another, potential precise future requirements of "guidance around corners" with regard to air-craft spacing will not be so satisfied.
A predetermined curved path is computed from one leg to the next leg in an RNAV system and steering signals are generated with regard to the curved path to guide the aircraft therealong. A bank angle bias command is ~ -utilized in defining the curved path during the leg transition. Cross track and track angle error signals are generated with regard to the curved path.
These signals may be applied to the automatic flight control system and/or ~
to the flight instruments to effect automatic control and to apprise the ~ -human pilot of the aircraft attitude and position with regard to the curved path so that corrective action may be effected.
~,;
Thus it is appreciated that the aforedescribed disadvantages of the prior art technique are eliminated in a manner to be clarified hereinafter.
The invention concerns apparatus for use in an area nayigation system for aircraft for controlling the transition of the aircraft from an ;
inbound course to an outbound course of a waypoint. The apparatus comprises a bank bias circuit for generating a bank angle command signal for rolling the aircraft to a desired bank attitude. The apparatus further includos a curved path computing circuit or computing a curved path from the inbound course to the outbound course in accordance with the bank angle command signal. A deviation circuit is included for generatlng deviation signals with respect to the curved path for constraining the aircraft to fly the curved path in executing the transition from the inbound to the outbound course.
~ igure 1 is a diagram illustrating geometrical parameters with regard to the curved transition path from an inbound course to an outbound course at a waypoint;
Figure 2 is a diagram similar to ~igure 1 illustrating further geometrical para~eters;
~igure 3 is a schematic block diagram of curved transitlon path ,~', .
, . . . . .
, ... . . .
`` 1~)84~3 generation and control apparatus for an aircraft area navigation system instrumented in accordance with the invention;
Figure 4 is a graph depicting the functional relationship of -desired bank angle with regard to ground speed and track change angle; and -2a-, 1~)8~ 3 1 Fig. 5 is a schematic block diagram o an alternative embodiment of the invention.
DESCRIPTION OF T~E PREFERRED EMBODIMENTS
Referring to Figs. 1 and 2, the lateral navigation para- -meters associated with transitioning from the inbound course to the outbound course of a waypoint of an RNAV system is illustrated. A waypoint 10 whose geographical location is determined in a well known manner by the r, ~ coordinates with respect to a VORTAC 11 has an inbound course 12 and an out-bound course 13 associated therewith. The inbound and outbound courses 12 and 13 with respect to north are designated ab ~ 1 and ~ 2 respectively. The geographical location of an aircraft 14 is determined from the VORTAC 11 in a conventional manner by the R, Q coordinates illustrated. The north and east components of the locations of the waypoint 10, the VORTAC 11 and the aircr~ft 14 with respect to each other are also illus-trated. For example, the north and east coordinate= of the aircrat 14 with respect to the VORTAC 11 are indicated in Fig.
2 as NAV and EAV respectively. Similarly the north and east coordinates of the waypoint 10 with re5pect to the VORTAC 11 are de~ignated as NWV and EWV respectively. Furthermore, NAW
and EAW designate the north and east coordinates o the aircrat 14 with respect to the waypoint 10.
In accordance wit~ the invention, a curved path 15 is generated along which to 1y the aircrat 1~ to eect a smooth and controlled transition from the inbound course 12 to the out~
bound cour~e 13. Preerably the curved path 15 is circular and ~, tangential to the inbound and outbound cour~es at points A and B respectively. ~ maximum aircrat ban~ anyle for the tran~ition ~o is determined as a function o aircrat ground ~peed and angular dierence between the inbound and outbound course~. With the 1 bank angle determined, a turning radius 16 or the curved path 15 is established in accordance with the maximum bank angle and the aircrat ground speed. The distance d is then determined which locates the point A on the inbound course 12 and in combination with the turn radius 16 locates the turn center for the curved path 15.
In order for the aircraft 14 to fly the path 15, the maximum bank angle is established at point A with the aircraft returning to zero bank angle at point B. However, since the aircraft 14 cannot be rolled into and out of t~e maximum bank attitude instantaneously, the associated roll command is , applied and removed at points A' and Bl respectively. The distances d' from the points A' and B' are determined rom considerations o~ passenger comfort and aircra~t roll response in accordance with the speciic aircraft to which the invention is applied.
With the aircraft 14 at the commanded bank angle at point A, the craft heading rate maintains the aircrat on the curved path 15 in an idealized calm air environment. However, due to winds, velocity changes, trim conditions, and the like, the aircrat 14 will deviate from the curved path 15. In order to correct or these deviations the cross track error (XTK) and the track angle error ~TKE) with respect to the curved path 15 are generated to steer the aircrat and provide pilot displays in a manner to be descri~ed~ For ease o lllustration with regard to Fig. 1, the aircrat 14 is oten considered to be located at point A. Thus the north and east coordinates o~ the aircra~t 14 with regard to the turn center are designated as NTCA and ETCA respectively. Similarly, NTCW and ETC~I designate the north and east components o t~e turn center with respect to the waypoint 10.
, . , ,: , .
`` l.V~G13 -1 Re~errinq to Fig. 3 with continued reference to Figs. 1 and 2, a schematic block diagram of apparatu~ for generating the curved path 15 and for controlling the aircraft 14 to fly therealong in transitioning from the inbound cour~e to the outbound course of the waypoint 10, is illustrated. The apparatu~
of Fig. 3 includes a plurality of function blocks that may be implemented by any of a variety of well known devices. For example, the function blocks may be instrumented by special purpose discrete analog or digital circuits or may alternatively be implemented by yeneral purpose digital computation apparatus.
A VOR re~eiver 20 provides thè VOR bearing J~ and a DME
receiver 21 provides the DME distance R in response to the signals from the VORTAC 11. The distance and bea~ing data are applied to a function block 22 wherein a function Fl converts the VO~ and DME data to the north and east coordinates, NAV
and EAV respectively, of the aircraft with respect to the VORTAC 11. Circuits for providing the function ~1 are well --known in ~he art and will not be described further herein for br0vity. The VOR and DME data are also applied to function blocks 23 and 24 wherein conventional circuitry implementing functions F2 and F3 provide the track angle and the ground speed V respectively of the aircrat 14. It will be appreciated that aircrat heading ~HDG) from a conventional compass system 29 and true airspeed (TAS) from a conventional air data system 28 may be utilized as inputs to the function block 2~ thereby generating a current and accurate value of the ground speed V.
The function F3 of the block 24 may be implemented as disclosed in U.S. patent 3,919,529 is~ued November 11, 1975 in the names o Donald H. Baker and ~arry ~. ~owe entltled "Radio Navigation System" and a~signed to the as~ign~e o the present invention.
~, , : . , .
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'; '";'''','' ' 1~ i13 1 The appara~us o~ Fig. 3 also lncludes a computer 25 for storing the navigational data with regard to the flight plan of the aircraft. For example, the computer 25 may be preloaded prior to a particular flight with the geographical locations of all of the waypoints along the ~light plan as well as the locations of the associated VORTACs. The computer is arranged in a conventional manner to provide the required data as the aircra~t executes the flight plan with regard to the sequentially - encountered waypoints. For example, with the aircra~t on the inbound course 12 of the waypoint 10, the computer 25 provides the pre-stored inbound and outbound courses ~1 and ~2 respectively ~or the waypoint 10 as well as the bearing O and distance r of the waypoint 10 with respect to the VORT~C 11.
The computer 25 also provides a control signal CCW in accord-ance whether the turn from the inbound course 12 to the out-bound course 13 is clockwise or counter-clockwise.
The computer 25 receives signals from a pilot manual data input device 26 by which the pilot may alter the data stored in the computer 25 or may enter new data therein. The device 26 may, for example, be implemented as a conventional alphanumeric and discrete data keyboard entry device for providing the data to the computer 25 in a well known manner~
The davice 26 may be utilized, ~or example, when the pilot wishes to deviate ~rom the ~light plan as stored in the computer 25.
The beæing and distance data (O, r) o~ the waypoint 10 with respect to the VORT~C 11 is applied to a ~unction block 27.
The block 27 in a well known manner instruments a conventional ~unction F4 ~or converting the O,r data to the north and east coordinates ~WV and EWV re~pect~vely o~ the waypoint with regard , 8~ L3 1 to the VORTAC. The signals NAV from the block 22 and NWV from the block 27 are applied to an algebraic summing device 30 to provide the north coordinate N~W of the aircraft 14 with respect to the waypoint lO. Similarly, the E~V signal from -the block 22 and the EWV signal from the block 27 are applied to an algebraic summing device 31 to provide the east coordinate EAW of the aircraft 14 with respect to the waypoint lO.
The inbound and outbound course signals ~ 1 and Y2 from the computer 25 as well as the ground speed signal V from the function block 24 are applied to a function block 32. The function block 32 provides the ma~imum desired bank angle 0m in accordance with a functional relationship F5 of the track change A~= ~2- ~1 and the ground speed V. The desired bank angle 0m is determined substantially as the pilot would from aircraft speed and the magnitude of the heading change. The faster the aircraft is moving, the lower the desired bank angle should be to provide a "smooth" ride. The larger the required heading change, the steeper the desired bank angle should be for prac~ical reasons. The bank angle command 0m is applied ;
at point ~' ~Fig. 1) such that the aircraft will have assumed the bank angle when it reaches point A, thus causing the craft to execute the curved path 15 in a manner to be describedO
It will be appreciated that the unctional relationship F5 implemented by the bloc~ 32 is ~elected in accordance with the particular characteristics o the aircra~t in which the system is in~talled. Reerriny to Fig. ~, typical functional relation~hip~ suitable or u~e in modern ~et transports are illu~trated. Functional relationship lines a, b, c, d and e repre~ent track change~ o 7 9O, 70, 50, 30 and ~ 10 respectively. The ifunctional relationship~ o~ Fig. ~ are "j, . . .. .. .. ... . . . . . .
1 readily implemented by such conventional devices as storage tables, diode matrices and the like. It will be appreciated that the block 32 also contains a difference circuit for obtaining a~= ~2- ~1 and this difference signal together with the ground speed V from the block 24 addresses the function generating apparatus to provide the associated value 0m as illustrated in Fig. 4.
Referring again to Fig. 3, the bank angle signal ~m from the block 32 and the ground speed signal V from the block 24 are applied to a function bloc~ 33 to generate the turn radius (TR) 16 (Fig. 1) for the circular path 15 in accordance with a function F6 as follows: 2 -~ .
F6 = TR = g tan ~
where g is the gravity constant. As previously described, it is appreciated that the function F6 is readily instrumented by any of a variety of suitable and well known analog and digital circuits.
The ~1 and ~ 2 signals rom the computer 25 as well as the turn radius signal TR from the function block 33 are applied 2~ to a function block 34 to generake a signal "d" in accordance with the distance between the point A and the waypoint 10 o Fig~ 1. The distance d is generated in accordance with a function F7 as ollows:
F7 - d = TR T~N 2 where, as previouslY discus5ed~ a ~= ~2- ~1' The implemented in any convenient manner in accordance with the unction F7 as discussed above with regard to t~e block 33.
The ~1 signal rom t~e computer 25, t~e turn radius TR
signal from the unction block 33 and the d ~ignal from the lVb~;13 1 function block 34 are applied to a function block 35 to generate the north and east coordinates of the turn center location with respect to the waypoint 10 as illustrated in Fig. 2, in accord- -ance with a function F8 as follows:
¦~TCW = -d cos ~1 ~ TR sin ~1 L~TCW = -d sin ~1 + TR cos ~1 The block 35 is implemented in any convenient manner as ~ -described above with respect to the block 33.
The NTCW signal from the block 35 and the N~W signal from the algebraic summing device 30 are combined in an alge~raic summing device 36 to provide the NTCA north coordinate of the aircraft location with respect to the turn center. In a ~;
similar manner, an algebraic summing device 37 combines the ETCW signal from the block 35 with the EAW signal from the algebraic summing device 31 to provide the ETC~ coordinate , -signal of the aircraft location with respect to the turn center.
The NTCA and ETCA signals are applied as inputs to a function block 40 wherein the quantity ~1 as illustrated in Fig. 1 is generated in accordance with a ~unction Fg as ollows:
Fg = ~1 = TAN 1 ETCA
where e1 represents the angular position of the aircraft on -the curved pat~ 15.
The track angle signal from the unction block 23, the CCW signal rom the computer 25 and the ~1 signal rom the function bloc~ 40, as well as a constant signal representing 90 are applied to a function block 41 to ~enerate the track angle error TKE in accordance with a function F1o as follows:
(TKE ~ ~ 90) - TR~CK ~NGLE or CCW tu~ns 10 ~ KE = (el~ 90) - TRACK ANGLE FOR CW turns , '' '' ',' ,, ,, ' ' , ' , ~ " ' ' ' ' , ' , , . . .
lV8¢~3 The TKE signal is applied to a line 42 as well as to a gain block 43. The gain block 43 applies a gain k2 to the TKE
signal in a well known manner, the gain being selected and .
conventionally adjusted in accordance with the aircraft characteristics and velocity..
The CCW signal from the computer 25, the turn radius signal TR ~rom the function block 33, the NTCA signal from the summing device 36 and the ETCA signal from the summing device 37 are applied to a function block 44 for generating 10 the cross track error signal ~KT in accordance with a function F11 as follows: .
XTK = ~NTCA + ETCA2 - TR for CCW turns XTK = TR - ~TCA ~ ETC~ for CW turns The XK~r signal is applied to a lead 45 as well as to a gain :
block 46 which inparts a gain k1 to the XKT signal in a manner similar to that described with respect to the block 43. The gain adjusted ~K signal from the block 46 is combined with the 0m signal from the block 32 in an algebraic summing device 47. The output of the algebraic summing device 47 and the gain 20 adjusted TKE signal rom the block 43 are combined in an algebraic summing device 50 to provide the system steering singal 0c on a lead 51. The 0c signal may be expressed as ollows:
0c '0~ ~ kl X~['K t k2 TKE
Preferably the steering signal 0c on the lead 51 is applied to the roll channel of the aircraft automatic flight control system and al~o to the lateral steering cue o~ the attitude director indicator of the 1ight director system o the crat. The track angle error signal TKE on the lead 42 is 30 pre:eerably applied to the commanded heading bug of the lVt~13 1 horizontal situation indicator instrument of the aircraft while the cross track error signal XTK on the lead 45 is applied to the lateral deviation indicator of the horizontal situation indicator. ~ --In operation, when the aircraft reaches the point A' (Fig. 1) as indicated by the signal d from the block 34 and the above discussed predetermined value of d', aircrat control is switched by conventional means not shown from the straight line control apparatus for the inbound course 12 (Fig. 1) to the curved path control apparatus of Fig. 3. The 0m signal from the block 32 applied via elements 47 and 50 to the lead 51 causes the aircraft to assume the bank angle ~m at the point ~.
The bank angle 0m then causes the craft to endeavor to turn ~ -about the turn center as determined by the NTCA and ETCA signals from the elements 36 and 37 respectively with a turn radius TR ~ -as determined by the block 33. When the craft is on the curved -path 15 the track angle error signal on the lead 42 and the cross track error signal on the lead 45 are both zero and thus the steering command 0c is equal to the bank angle command 0m which tends to maintain the craft on the curved path 15 by maintaining the craft banksd at the angle 0m. When the craft departs rom the curved path 15, due or example to transients .
such as wind and the li~c~ or aircraft configuration changes, t~e combination of the track angle error rom the block 41 and the cross track error slgnal from the block 44 combined in the steering command 0c tend to steer the aircraft back to the curved path 15.
~ hen the craft reaches the point ~' (Fig. 1) as deter-minea from the computed value of ~ and the predetermined value o dl a~ ai~cUssea above, aircraf~ control i5 ~witched ~
, . :. ,. ", . ~ " , . . . . . .
.... .. . . . . . . .
" , ' , .. . . . .
:l~J~ 13 1 means not shown -Erom the curved path control apparatus o~ -Fig. 3 to the straight line control apparatus with regard to the outbound course 13 and thus the aircraft rolls back to wings level flight by the time it reaches point B, completing the transition from the inbound course 12 to the outbound course 13 of the waypoint 10.
It will be appreciated that since the cross track error from the block 44 is applied via the lead 45 to the lateral deviation cue of the horizontal situation indicator (HSI) and since the error is computed with respect to the curved path 15 as the aircraft executes the course transition, it is merely necessary that the pilot maintains the lateral deviation indicator centered in order to make good the desired curved -path. Similarly, since the track angle error from the block 41 is applied via the lead 42 to the commanded heading bug of the HSI and the error is computed with respect to the curved path 15, the commanded heading bug remains centered under the index of the HSI as the craft executes the course transition along the curved path 15. The turn rate o the cra~t along the curved path 15 is displayed to the pilot by reason o the compass card o the HSI slewing under the commanded heading bug at a rate equal to the turning rate o the cra~t until the new course is achieved at point B o Fig. 1. Thus the present invention guides the aircra~t in making turns by utilizing the same ~teering laws and outputs as when flying straight tracks, and additionally permit~ consistent HSI display rules. Thus it i~ appreciated that the HSI di~plays to the pilot a clear and uninterrupted presentation o the system perormance throughout the tran8ition.
Reerring now to Fig. 5 in w~lich like reerence numerals ~, . ..
' ', ' . "~ '' ', "",~ ' " ',, ' ', , ' .
~o~
1 indicate like components with respect to Fig. 3, an alternative embodiment of the invention is illustrated. The VOR receiver 20, the DME receiver 21 and the pilot manual data input device --- -26 provide inputs to a programmed general purpose digital computer 60, the data inputs from the blocks 20, 21 and 26 being similar to those described above with respect to Fig. 3. It will be appreciated that conventional analog-to-digital conver-ters (not shown) may be utilized at the input interface of the computer 60 where appropriate. The computer 60 is programmed to provide the track angle error signal TKE, the cross track error XTK and the steering signal 0c on the leads 42, 45 and 51 respectively, the nature and purposes of these signals having been previously described with respect to Fig. 3.
The computer 60 is programmed in a conventional and well known manner to provide the N~V, FAV, track angle and ground speed (V) signals as described above from the VOR and DME data.
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Additionally, in a manner similar to that described above with regard to the computer 25 o Fig. 3, the computer 60 stores the ~ 2~ ~ r and CCW data with regard to the VORT~Cs and waypoints of the flight plan. The5e data may also be altered and supplemented by the pilot manual dcata input device 26 ln the manner previously described. The computer 60 is furthermore programmed in a conventional and well ~nown manner to provide the NWV and ~WV signals ~rom the ~ and r data stored therein~
With the above described parcameters internally available, the computer 60 is programmed to provide the 0c~ the X~K and the TKæ signal~ in accordance with the following program Chapin Chart:
1()8~ i3 PROGRAM CHAPIN CHART
. . . . . . .... ._ __ . .. .. : .
NAW = NAV -- NWV
. _. _ . . . .
EAW - EAV - EWV
. . . _ . . .
~ 2 ... . . . . ..... ____ . . .. _ _._ _ __ 0m= ~ (V~ Q~) .
g t~n 0m _ d = TR * TAN a Yl NTCW = -d*cos ~1 - TR sin 1 - I : - :
ETCW = -d*sin ~Yl + TR*cos ~1 ~TCA = NTCW - NAW ~ .
- I
ETCA = ETCW -- EAW
~:
~ = T~-l NTCA
: ~ - ~ I . .
: : Tru~ CCW = 1~ ~alse¦
~ ~ XTK = ~CA2 -TR };~K = TR - ~/~rCA~ ETCAZ
: . . . . I
1 : rKE = ~Ql-90)- TP~ACK ANGI~E TKE = t0l~9O)- TRACK ANGLE
~ . . .. . . . _ ___ I
0c ~ 0m ~ kl *~K ~ k2*TKE
' . ' ~.
:
. ..
--1~
- .
. . . .
,~, , ',"' ',, ' . ' ' .
lU6~
1 As is known to those skilled in the art, the program chapin chart represents a convenient format, similar to the familiar program flow chart, for organizing the details of the computations to be performed preparatory to coding by the programmer. It will furthermore be readily appreciated by those skilled in the art that coding is generated in a routine manner from the above chapin chart in any convenient programming language associated with the computer utilized and will not be further described herein for brevity. It will be appreciated that the 0m data is computed in a manner similar to that described above with regard to the function block 32 of Fig.
3. It will furthermore be appreciated that the digital values f 0c' XTK and TKE are converted by conventional digital-to-analog devices (not shown) to provide the associated analog ~ -signals as required.
The steering signal 0c is applied to the roll channel of the automatic flight control system (AFCS) 61 of the aircraft to steer the craft along the curved path 15 of Fig. 1.
~ccordingly, the output of the AFCS 61 is applied through appropriate linkages 62 and a mechanical summing device 63 to control the aircraft roll attitude ~urfaces. The ~teering signal 0c i8 also applied to the aircraft flight director 64 which includes the conventional attitude director indicator 65 with the roll command signal 0c being applied to the lateral Rteering cue o the attitude dlrector indicator 65.
In a conventional manner the pilot 66 applies manual control signals ~ia appropriate controls and linkages 67 to steer the aircra~t along t~e curved path 15 b~ maintaining the lateral steering cue of the attltude director indicator 65 centared in a well known manner.
~08~13 1 The cross track error signal XTK on the lead 45 and the track angle error signal TKE on the lead 42 are applied to the horizontal situation indicator (HSI) 70 of the aircraft.
The cross track error signal is applied to ~he lateral devi-ation bar and the track angle error signal is applied to the commanded heading bug of the HSI 70. It will be appreciated that the pilot 66, in addition to his being apprised o~ the horizontal situation of the aircraft by observation of the -instrument 70, may also utilize the displayed information to steer the aircraft along the curved path 15 of Fig. 1 via the controls and linkages 67. For example, by maintaining the commanded heading bug centered under the HSI index and main-taining the lateral deviation bar centered, the aircraft is steered to make good the curved path 15.
It will be appreciated from the foregoing that the elements of the above described embodiments of the invention that generate the turn center, turn radius and el parameters comprise means for generating a curved path with respect to the inbound and outbound courses of the waypoint. It will furthermore be appreciated that the elements ~or generating tbe cros6 track and track angle errors a6 well as the steering signal 0c compri6e mean6 ~or generating deviation signals with regard to t~e curved path or steering the aircraft there-along. It wlll al~o be appreciated that although the above de6cribed embodlment~ of the invention were explained in terms of a circul æ path, any smookh curve may be itted between the inbound and outbound cour6e6 and deviation ~ignals generated with re~pect thereto to ~teer the aircra~t along the computed curve.
It iB appreciated rom the foregoing that by utili~ing the present invention during leg ~witching in an RNAV 6ystem, -16_ .......
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1 the aircraft is guided through the transition using the normal piloting techniques associated with straight line flight. The cross track error and track angle error are computed with respect to the curved path and are utilized in computing the -bank command ~c for the AFCS and the flight director. Since utilizing the track angle and cross track errors with respect to the curved path would result in a zero bank command when the aircraft is making good the path, the bank bias command signal 0m is mixed with the computation at the point A' assuring that the aircraft maintains the proper bank angle when making good the desired cur~ed path. The bank bias is removed at the point B' and the cross track and track angle errors with respect to the outbound track are utilized for the computations resulting in a steering signal that rolls the aircraft level at the point B in a smooth transition from the curved path to the next leg. Since the cross track and track angle errors are computed with respect to the predetermined curved path and are displayed on the HSI, the pilot is permitted to maintain the lateral deviation and heading command bug aligned, thereby allowing for manual leg-to-leg transltions without overshoot or undershoot of the next leg. Therefore, the RNAV system utiliz-ing the present invention provides controlled guidanae during the transition from one leg to the next of the aircraft flight plan. By thus providing a "steered" turn, the pilot is-~etter able to maintain cognizance of his position when transitioning from one track to another, especially if track changes occur often, aB in terminal areas with the track during transition being accurately controlled. Thi~ type of controlled guidance may become a re~uirement of a~iation regulatory agencies for RN~V ~ystem~ to provide accurate ~pacing of aircraft during turns aB well as on straight legs.
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lU~ L3 1 Thus the present invention achieves steering the aircraft through the transition from one RNAV leg to the next using minimum air space with a smooth easily identifiable manual and/or automatic command. The desired aircraft bank limits, velocity and transition heading change are utilized to compute the curved path which is tangential to both RNAV legs at the entrance and exit points of the planned maneuver. Additionall~, the present in~ention reduces overshoot and el~minates large deviation presentations to the pilot by providing an easily definable RNAV leg transition. The curved path is completely predictable and therefore air space tolerances are defined along the curved path. The invention, therefore, eliminates the large unpredictable air space due to l'S" turning and overshoots necessitated in present day systems.
.... .
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The steering signal 0c is applied to the roll channel of the automatic flight control system (AFCS) 61 of the aircraft to steer the craft along the curved path 15 of Fig. 1.
~ccordingly, the output of the AFCS 61 is applied through appropriate linkages 62 and a mechanical summing device 63 to control the aircraft roll attitude ~urfaces. The ~teering signal 0c i8 also applied to the aircraft flight director 64 which includes the conventional attitude director indicator 65 with the roll command signal 0c being applied to the lateral Rteering cue o the attitude dlrector indicator 65.
In a conventional manner the pilot 66 applies manual control signals ~ia appropriate controls and linkages 67 to steer the aircra~t along t~e curved path 15 b~ maintaining the lateral steering cue of the attltude director indicator 65 centared in a well known manner.
~08~13 1 The cross track error signal XTK on the lead 45 and the track angle error signal TKE on the lead 42 are applied to the horizontal situation indicator (HSI) 70 of the aircraft.
The cross track error signal is applied to ~he lateral devi-ation bar and the track angle error signal is applied to the commanded heading bug of the HSI 70. It will be appreciated that the pilot 66, in addition to his being apprised o~ the horizontal situation of the aircraft by observation of the -instrument 70, may also utilize the displayed information to steer the aircraft along the curved path 15 of Fig. 1 via the controls and linkages 67. For example, by maintaining the commanded heading bug centered under the HSI index and main-taining the lateral deviation bar centered, the aircraft is steered to make good the curved path 15.
It will be appreciated from the foregoing that the elements of the above described embodiments of the invention that generate the turn center, turn radius and el parameters comprise means for generating a curved path with respect to the inbound and outbound courses of the waypoint. It will furthermore be appreciated that the elements ~or generating tbe cros6 track and track angle errors a6 well as the steering signal 0c compri6e mean6 ~or generating deviation signals with regard to t~e curved path or steering the aircraft there-along. It wlll al~o be appreciated that although the above de6cribed embodlment~ of the invention were explained in terms of a circul æ path, any smookh curve may be itted between the inbound and outbound cour6e6 and deviation ~ignals generated with re~pect thereto to ~teer the aircra~t along the computed curve.
It iB appreciated rom the foregoing that by utili~ing the present invention during leg ~witching in an RNAV 6ystem, -16_ .......
. .
1 the aircraft is guided through the transition using the normal piloting techniques associated with straight line flight. The cross track error and track angle error are computed with respect to the curved path and are utilized in computing the -bank command ~c for the AFCS and the flight director. Since utilizing the track angle and cross track errors with respect to the curved path would result in a zero bank command when the aircraft is making good the path, the bank bias command signal 0m is mixed with the computation at the point A' assuring that the aircraft maintains the proper bank angle when making good the desired cur~ed path. The bank bias is removed at the point B' and the cross track and track angle errors with respect to the outbound track are utilized for the computations resulting in a steering signal that rolls the aircraft level at the point B in a smooth transition from the curved path to the next leg. Since the cross track and track angle errors are computed with respect to the predetermined curved path and are displayed on the HSI, the pilot is permitted to maintain the lateral deviation and heading command bug aligned, thereby allowing for manual leg-to-leg transltions without overshoot or undershoot of the next leg. Therefore, the RNAV system utiliz-ing the present invention provides controlled guidanae during the transition from one leg to the next of the aircraft flight plan. By thus providing a "steered" turn, the pilot is-~etter able to maintain cognizance of his position when transitioning from one track to another, especially if track changes occur often, aB in terminal areas with the track during transition being accurately controlled. Thi~ type of controlled guidance may become a re~uirement of a~iation regulatory agencies for RN~V ~ystem~ to provide accurate ~pacing of aircraft during turns aB well as on straight legs.
,; ,. . .
lU~ L3 1 Thus the present invention achieves steering the aircraft through the transition from one RNAV leg to the next using minimum air space with a smooth easily identifiable manual and/or automatic command. The desired aircraft bank limits, velocity and transition heading change are utilized to compute the curved path which is tangential to both RNAV legs at the entrance and exit points of the planned maneuver. Additionall~, the present in~ention reduces overshoot and el~minates large deviation presentations to the pilot by providing an easily definable RNAV leg transition. The curved path is completely predictable and therefore air space tolerances are defined along the curved path. The invention, therefore, eliminates the large unpredictable air space due to l'S" turning and overshoots necessitated in present day systems.
.... .
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~0
Claims (21)
1. In an area navigation system for aircraft, apparatus for transitioning the aircraft from an inbound to an outbound course of a waypoint comprising bank bias means for generating a predetermined bank angle command signal for rolling said aircraft to a predetermined desired bank attitude, curved path means for computing a circular path from said inbound course to said outbound course tangentially thereto and having a turn radius in accordance with said bank angle command signal, and deviation means for generating deviation signals with respect to said circular path for constraining said aircraft to fly said circular path in transitioning from said inbound to said outbound course.
2. The apparatus of claim 1 in which said curved path means comprises turn center means for generating turn center signals for said circular path, turn radius means coupled to said bank bias means for generating a turn radius signal for said circular path in accordance with said bank angle command signal, and angular position means responsive to said turn center signals for generating an angular position signal representative of the angular position of said aircraft on said circular path.
3. The apparatus of claim 2 in which said turn center means comprises difference means for providing a difference signal representative of the difference between said inbound and out-bound courses, distance means responsive to said turn radius signal and said difference signal for providing a distance signal representative of the distance of said waypoint to the point of tangency of said circular path on said inbound course, and turn center computing means responsive to said distance signal, said turn radius signal and a signal representative of said inbound course for generating said turn center signals in accordance therewith.
4. The apparatus of claim 3 in which said difference means comprises means for computing the function .DELTA.?=?2-?1, said distance means comprises means for computing the function and said turn center computing means comprises means for computing the function where = said inbound and outbound courses respectively = said difference signal TR = said turn radius signal d = said distance signal NTCW, ETCW = said turn center signals representing the north and east coordinates of said turn center with respect to said waypoint respectively.
5. The apparatus of claim 2 in which said turn radius means comprises means for providing a velocity signal representative of the speed of said aircraft, and means for providing said turn radius signal in accordance with said bank angle command signal and said velocity signal.
6. The apparatus of claim 5 in which said turn radius means comprises means for computing the function where TR = said turn radius signal V = said velocity signal ?m = said bank angle command signal g = the gravity constant.
7. The apparatus of claim 3 further including VOR/DME
computing means for providing first position signals repre-sentative of the position of said aircraft with respect to a VOR/DME station, waypoint computing means for providing second position signals representative of the position of said waypoint with respect to said VOR/DME station, and combining means responsive to said first and second position signals and said turn center signals for providing further position signals representative of the position of said aircraft with respect to said turn center, said angular position means being responsive to said further position signals for generating said angular position signal.
computing means for providing first position signals repre-sentative of the position of said aircraft with respect to a VOR/DME station, waypoint computing means for providing second position signals representative of the position of said waypoint with respect to said VOR/DME station, and combining means responsive to said first and second position signals and said turn center signals for providing further position signals representative of the position of said aircraft with respect to said turn center, said angular position means being responsive to said further position signals for generating said angular position signal.
8. The apparatus of claim 7 in which said combining means comprises first combining means for combining said first and second position signals for providing third position signals representative of the position of said aircraft with respect to said waypoint, and second combining means for combining said third position signals and said turn center signals for providing said further position signals.
9. The apparatus of claim 8 in which said difference means comprises means for computing the function .DELTA.?=?2-?1, said distance means comprises means for computing the function , and said turn center computing means comprises means for computing the function NTCW = -d cos ? 1 - TR sin ? 1 ETCW = -d sin ? 1 + TR cos ? 1 where ?l, ?2 = said inbound and outbound courses respectively .DELTA.? = said difference signal TR = said turn radius signal d = said distance signal NTCW, ETCW = said turn center signals representing the north and east coordinates of said turn center with respect to said waypoint respectively.
10. The apparatus of claim 9 in which said VOR/DME computing means comprises means for providing first position signals NAV and EAV representative of the north and east coordinates respectively of said position of said aircraft with respect to said VOR/DME station, said waypoint computer means comprises means for providing second position signals NWV
and EWV representative of the north and east coordinates respectively of said position of said waypoint with respect to said VOR/DME station, said first combining means comprises means for computing the function NAW = NAV - NWV
EAW = EAV - EWV, and aid second combining means comprises means for computing the function NTCA = NTCW - NAW
ETCA = ETCW - EAW
where NAW, EAW = said third position signals representing the north and east coordinates respectively of said position of said aircraft with respect to said waypoint and NTCA, ETCA =
said further position signals representing the north and east coordinates respectively of said position of said aircraft with respect to said turn center.
and EWV representative of the north and east coordinates respectively of said position of said waypoint with respect to said VOR/DME station, said first combining means comprises means for computing the function NAW = NAV - NWV
EAW = EAV - EWV, and aid second combining means comprises means for computing the function NTCA = NTCW - NAW
ETCA = ETCW - EAW
where NAW, EAW = said third position signals representing the north and east coordinates respectively of said position of said aircraft with respect to said waypoint and NTCA, ETCA =
said further position signals representing the north and east coordinates respectively of said position of said aircraft with respect to said turn center.
11. The apparatus of claim 10 in which said angular position means comprises means for computing the function ?1 = tan where ?1 = said angular position signal.
12. The apparatus of claim 1 in which said deviation means comprises cross track error means coupled to said curved path means for generating a cross track error signal with respect to said curved path, track angle error means coupled to said curved path means for generating a track angle error signal with respect to said curved path, and steering signal means responsive to said cross track error signal, said track angle error signal and said bank angle command signal for providing a steering signal in accordance therewith with respect to said curved path, said cross track error signal, said track angle error signal and said steering signal comprising said deviation signals.
13. The apparatus of claim 12 further including an automatic flight control system responsive to said steering signal for controlling said aircraft about the roll axis thereof in response to said steering signal.
14. The apparatus of claim 12 further including a flight director system responsive to said steering signal and including an attitude director indicator with the lateral steering cue thereof driven by said steering signal.
15. The apparatus of claim 12 further including a horizontal situation indicator responsive to said cross track error signal and said track angle error signal with the lateral deviation and the commanded heading cues thereof driven by said cross track error signal and said track angle error signal respectively.
16. The apparatus of claim 7 including further VOR/DME com-puting means for providing a track angle signal representative of the track angle of said aircraft.
17. The apparatus of claim 16 in which said deviation means comprises cross track error means responsive to said further position signals and said turn radius signal for generating a cross track error signal in accordance therewith with respect to said curved path, track angle error means responsive to said angular position signal and said track angle signal for generating a track angle error signal in accordance therewith with respect to said curved path, and steering signal means responsive to said cross track error signal, said track angle error signal and said bank bias command signal for providing a steering signal in accordance therewith with respect to said curved path, said cross track error signal, said track angle error signal and said steering signal comprising said devia-tion signals.
18. The apparatus of claim 11 including further VOR/DME com-puting means for providing a track angle signal representative of the track angle of said aircraft.
19. The apparatus of claim 18 in which said deviation means comprises cross track error means responsive to said further position signals and said turn radius signal for generating a cross track error signal in accordance therewith with respect to said curved path, track angle error means responsive to said angular position signal and said track angle signal for generating a track angle error signal in accordance therewith with respect to said curved path, and steering signal means responsive to said cross track error signal, said track angle error signal and said bank bias command signal for providing a steering signal in accordance therewith with respect to said curved path, said cross track error signal, said track angle error signal and said steering signal comprising said deviation signals.
20. The apparatus of claim 19 in which said cross track error means comprises means for computing the function XTK = for clockwise turns XTK = for counterclockwise turns, said track angle error means comprises means for computing the function TKE =(?1+90°) - TRACK ANGLE for clockwise turns TKE =(?1-90°) - TRACK ANGLE for counterclockwise turns, and said steering signal means comprises means for computing the function ?c=?m + k1 XTK = k2 TKE
where XTK = said cross track error signal TKE = said track angle error signal TRACK ANGLE z said track angle of said aircraft ?c = said steering signal ?m = said bank angle command signal k1, k2 = gain terms.
where XTK = said cross track error signal TKE = said track angle error signal TRACK ANGLE z said track angle of said aircraft ?c = said steering signal ?m = said bank angle command signal k1, k2 = gain terms.
21. The apparatus of claim 1 in which said bank bias means comprises means for providing a velocity signal representative of the speed of said aircraft, difference means for providing a difference signal representative of the difference between said inbound and outbound courses, and bank bias function means responsive to said velocity signal and said difference signal for providing said bank angle command signal in accordance therewith.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/581,987 US3994456A (en) | 1975-05-29 | 1975-05-29 | Steered lateral course transition control apparatus for aircraft area navigation systems |
| US581,987 | 1975-05-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1084613A true CA1084613A (en) | 1980-08-26 |
Family
ID=24327387
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA247,526A Expired CA1084613A (en) | 1975-05-29 | 1976-03-10 | Steered lateral course transition control for aircraft area navigation systems |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US3994456A (en) |
| JP (1) | JPS51146099A (en) |
| BR (1) | BR7602979A (en) |
| CA (1) | CA1084613A (en) |
| DE (1) | DE2624095A1 (en) |
| FR (1) | FR2331084A1 (en) |
| GB (1) | GB1524261A (en) |
| IL (1) | IL49594A (en) |
| IT (1) | IT1066099B (en) |
Families Citing this family (22)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4021009A (en) * | 1975-07-24 | 1977-05-03 | Sperry Rand Corporation | Vertical path control for aircraft area navigation system |
| US4212067A (en) * | 1978-07-20 | 1980-07-08 | General Aviation Electronics, Inc. | Navigating device |
| GB8425442D0 (en) * | 1984-10-09 | 1984-11-14 | Devon County Council Burns R | Automatic vehicle control method |
| US4622667A (en) * | 1984-11-27 | 1986-11-11 | Sperry Corporation | Digital fail operational automatic flight control system utilizing redundant dissimilar data processing |
| US4692869A (en) * | 1985-03-28 | 1987-09-08 | The Boeing Company | Aircraft navigational systems and methods for creating navigational guidepoints |
| US4799159A (en) * | 1985-05-30 | 1989-01-17 | Honeywell Inc. | Digital automatic flight control system with disparate function monitoring |
| US4713757A (en) * | 1985-06-11 | 1987-12-15 | Honeywell Inc. | Data management equipment for automatic flight control systems having plural digital processors |
| US4787041A (en) * | 1985-08-01 | 1988-11-22 | Honeywell | Data control system for digital automatic flight control system channel with plural dissimilar data processing |
| DE3537730A1 (en) * | 1985-10-23 | 1987-04-30 | Maximilian Dr Waechtler | Device for automatically steering towards a target point |
| US4999782A (en) * | 1989-05-03 | 1991-03-12 | Honeywell Inc. | Fixed curved path waypoint transition for aircraft |
| US5646854A (en) * | 1989-11-14 | 1997-07-08 | Honeywell Inc. | Lateral guidance transition control apparatus for aircraft area navigation systems |
| FR2737795B1 (en) * | 1995-08-10 | 1997-10-24 | Aerospatiale | METHOD AND DEVICE FOR GUIDING A MOBILE |
| US6092007A (en) * | 1998-04-29 | 2000-07-18 | Sikorsky Aircraft Corporation | Aircraft course correction for wind and fuzzy logic course intercept profile based upon accuracy and efficiency |
| FR2803655B1 (en) * | 2000-01-07 | 2002-06-14 | Thomson Csf Sextant | FLIGHT CALCULATOR SMOOTHING THE TRAJECTORY OF AN AIRCRAFT ON SEVERAL SEQUENCES |
| US20050162425A1 (en) * | 2004-01-23 | 2005-07-28 | Kyle Henry M. | Dynamic mapping tool |
| US20090177339A1 (en) * | 2005-03-03 | 2009-07-09 | Chen Robert H | Optimization and Mechanization of Periodic Flight |
| FR2916287B1 (en) * | 2007-05-15 | 2014-06-27 | Thales Sa | METHOD FOR TRACING A TRACK PORTION OF AN AIRCRAFT COMPRISING A CONSTANT RING CIRCLE ARC |
| US9250098B2 (en) * | 2008-12-23 | 2016-02-02 | Honeywell International Inc. | Systems and methods for displaying heading-based leg symbology |
| KR101145112B1 (en) * | 2010-05-11 | 2012-05-14 | 국방과학연구소 | Steering control device of autonomous vehicle, autonomous vehicle having the same and steering control method of autonomous vehicle |
| CN104615144B (en) * | 2015-01-30 | 2017-06-13 | 天津大学 | Hypersonic aircraft reentry trajectory method for on-line optimization based on goal programming |
| CN111240362B (en) * | 2020-01-20 | 2023-04-28 | 湖北三江航天红峰控制有限公司 | Control method and device for intelligently guiding aircraft to turn |
| CN112278336B (en) * | 2020-11-03 | 2022-03-22 | 北京空间飞行器总体设计部 | High-speed reentry heat flow flight test verification method |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3355126A (en) * | 1966-09-06 | 1967-11-28 | Collins Radio Co | Radio beam capture circuit for aircraft guidance |
| US3635428A (en) * | 1969-01-17 | 1972-01-18 | Sperry Rand Corp | Automatic pilot for navigable craft |
| US3786505A (en) * | 1970-03-04 | 1974-01-15 | J Rennie | Self-contained navigation system |
| US3739382A (en) * | 1970-09-08 | 1973-06-12 | Mitchell Ind Inc | Aircraft lateral guidance system |
| US3848114A (en) * | 1972-01-12 | 1974-11-12 | Sperry Rand Corp | Control system for providing a spiral flight path to a radio beacon |
| US3788579A (en) * | 1972-03-10 | 1974-01-29 | Bendix Corp | Aircraft control system using inertially sensed data |
| US3814911A (en) * | 1972-12-26 | 1974-06-04 | King Radio Corp | Method and apparatus for intercepting a radio defined course |
-
1975
- 1975-05-29 US US05/581,987 patent/US3994456A/en not_active Expired - Lifetime
-
1976
- 1976-03-10 CA CA247,526A patent/CA1084613A/en not_active Expired
- 1976-05-12 BR BR7602979A patent/BR7602979A/en unknown
- 1976-05-17 IL IL49594A patent/IL49594A/en unknown
- 1976-05-26 IT IT49677/76A patent/IT1066099B/en active
- 1976-05-27 GB GB22022/76A patent/GB1524261A/en not_active Expired
- 1976-05-27 JP JP51061687A patent/JPS51146099A/en active Granted
- 1976-05-28 FR FR7616157A patent/FR2331084A1/en active Granted
- 1976-05-28 DE DE19762624095 patent/DE2624095A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| IL49594A0 (en) | 1976-07-30 |
| JPH0133398B2 (en) | 1989-07-13 |
| BR7602979A (en) | 1977-02-15 |
| FR2331084B1 (en) | 1982-07-23 |
| FR2331084A1 (en) | 1977-06-03 |
| JPS51146099A (en) | 1976-12-15 |
| US3994456A (en) | 1976-11-30 |
| DE2624095A1 (en) | 1976-12-09 |
| DE2624095C2 (en) | 1987-03-05 |
| GB1524261A (en) | 1978-09-13 |
| IT1066099B (en) | 1985-03-04 |
| IL49594A (en) | 1978-04-30 |
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